Method for decoding address in pre-groove data of an optical disc drive

ABSTRACT

A method for optical drive decoding of address in pre-groove (ADIP) data is provided to decode an input wobble signal to an ADIP unit signal. The method includes generating a wobble carrier frequency signal having the same phase with the wobble signal, multiplying the wobble carrier frequency signal by the input wobble signal to generate a product signal, accumulating the value of the product signal in each clock to generate a quotient summation signal, determining the phase change of the input wobble signal according to the value of the quotient summation to generate a phase change signal, and generating the ADIP unit signal by comparing the phase change signal with a plurality of ADIP patterns.

BACKGROUND OF INVENTION

1. Field of the Invention

The present invention relates to a method for decoding an address inpre-groove (ADIP) data of an optical disc drive, and more specifically,to a method for decoding ADIP data by comparing ADIP data with signalsgenerated by quotient summation.

2. Description of the Prior Art

Please refer to FIG. 1 showing a conventional optical drive reading atrack 12 of an optical disc 10. In the DVD+R/RW disc 10, the track 12can be divided into two types: a data track 14 for recording data and awobble track 16 for recording ADIP data corresponding to sections on thedisc. The data track 14 spirals around the center of the disc 10following the track 12, and the wobble tracks 16 also spiral around thecenter of the disc 10, however, they wobble up and down in a smallamplitude. In addition, the wobble tracks 16 are continuous protrudingtracks, and the data track 14 is located in the groove formed betweentwo wobble tracks 16. The data track 14 has continuous record signals 18(corresponding to pits) of different lengths and differentcharacteristics of reflection. These record signals 18 representdifferent data information, thus the disc 10 can record data bycontrolling the length of the record signal 18.

A pickup head 20 of an optical disc drive includes four sensors Sa, Sb,Sc, Sd for reading data in the wobble tracks 16. Since thecharacteristics of reflection of the groove and the protruding tracksdiffer from each other, the reflection sensed by the sensors Sa, Sb, Sc,Sd differs accordingly, thus wobble signals can be obtained bycalculating sensed values of the sensors Sa, Sb, Sc, Sd. As the disc 10rotates, the pickup head 20 follows the disc 10 along the directionshown by arrow 22 to read the sensed values along the track 12. Forinstance, when the pickup head 20 is located at P1, the position of thesensors Sa, Sd corresponds to the groove of the data track 14, and theposition of the sensors Sb, Sc corresponds to the protrusion of thewobble track 16. When the pickup head 20 is located at P2, the sensorsSa, Sd, originally located over the groove, move to the position overthe protrusion of the wobble track 16. Additionally, the sensors Sb, Sc,originally located over the protrusion of the wobble track 16, move tothe position over the groove of the data track 14. Accordingly, thesensed value as well as the wobble signal change. In such a manner, thepickup head 20 generates the wobble signals according to the wobbletrack, and the wobble signals can be decoded into address in pre-groove(ADIP) data.

Please refer to FIG. 2 to FIG. 4 respectively showing conventionalwobble signals 24, 26, 28. Every two record sections on the disc 10correspond to 93 wobble periods, wherein 8 wobble periods record theADIP data using phase modulation (PM). As shown in FIG. 2, the wobblesignal 24 includes 8 wobble periods W0, W1, W2, W3, W4, W5, W6, W7recording the ADIP data using phase modulation. In the wobble periodsW0, W4, the phase of the wobble signal 24 changes by 180 degrees, and inthis case, the wobble signal 24 corresponds to an ADIP sync unit. Asshown in FIG. 3, the wobble signal 26 includes 8 wobble periods W0, W1,W2, W3, W4, W5, W6, W7 recording the ADIP data using phase modulation.In the wobble periods W0, W1, W6, the phase of the wobble signal 26changes by 180 degrees, and in this case, the wobble signal 26corresponds to an ADIP data unit being “0”. As shown in FIG. 4, thewobble signal 28 includes 8 wobble periods W0, W1, W2, W3, W4, W5, W6,W7 recording the ADIP data using phase modulation. In the wobble periodsW0, W1, W4, W6, the phase of the wobble signal 28 changes by 180degrees, and in this case, the wobble signal 28 corresponds to an ADIPdata unit being “1”.

As described above, the decoding of ADIP data plays an important rolewhen burning the DVD+R/RW disc. The ADIP data includes all theinformation on the DVD+R/RW disc, and the frequency of the wobble signalrepresents the linear speed of disc rotation. For constant linearvelocity (CLV) reading, the wobble signals are utilized as feedbacksignals to a spindle motor. And for constant angular velocity (CAV), thewobble signals are used to generate writing clocks. However, the wobblesignals may be interfered with due to defects on the disc, noise, orlaser power fluctuations, so that the ADIP data may be lost or thefrequency of the wobble signals may be unstable.

SUMMARY OF INVENTION

It is therefore a primary objective of the present invention to providea method for decoding ADIP data of an optical disc drive, in order tosolve the problems in the prior art.

Briefly summarized, the present invention provides a method for decodingaddress data being ADIP data of an optical disc drive, for decoding aninput wobble signal into an ADIP unit signal. The optical disc driveincludes a phase lock loop, a cosine signal generator, a multiplier, anaccumulator, a phase data processor and an ADIP unit detector. Themethod includes (a) converting a wobble carrier frequency signal outputby the phase lock loop into a wobble carrier frequency signal with thesame phase as the input wobble signal, by the cosine signal generator,(b) multiplying the wobble frequency signal output by the cosine signalgenerator with the input wobble signal to obtain a product signal, bythe multiplier, (c) accumulating the product signals at each clock toobtain a quotient summation signal, by the accumulator, (d) determiningphase changes of the input wobble signal according to whether thequotient summation signal is positive or negative to obtain a phasechange signal, by the phase data processor, and (e) comparing the phasechange signal with the plurality of ADIP patterns by the ADIP unitdetector, and determining an ADIP unit signal according to the ADIPpattern closest to the phase change signal.

The present invention further provides a device to implement the methodmentioned above.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a conventional optical drive reading a track of anoptical disc.

FIG. 2 illustrates a conventional wobble signal corresponding to ADIPunit representing SYNC.

FIG. 3 illustrates a conventional wobble signal corresponding to ADIPunit representing “0”.

FIG. 4 illustrates a conventional wobble signal corresponding to ADIPunit representing “1”.

FIG. 5 is a block diagram of an ADIP decoder according to the presentinvention.

FIG. 6 illustrates the signals shown in FIG. 5.

FIG. 7 illustrates a fuzzy compare method according to the presentinvention.

FIG. 8 illustrates a relative shape compare method according to thepresent invention.

FIG. 9 is a flowchart according to the present invention.

FIG. 10 illustrates a result table for experiments performed accordingto the present invention.

DETAILED DESCRIPTION

Please refer to FIG. 5 showing a block diagram of an ADIP decoder 30according to the present invention. The ADIP decoder 30 includes a phaselock loop 32, a decoding circuit 40, a writing clock generating circuit34, and a protection circuit 36. The phase lock circuit 32 generates awobble carrier frequency signal according to an input wobble signal, todecode data, control a spindle motor and generate the writing clockaccording to the wobble carrier frequency signal. The decoding circuit40 generates an ADIP unit signal (0, 1, or SYNC), and then generates awobble address through an error correction code (ECC) block 38. Thewriting clock generating circuit 34 generates clocks required whenwriting the disc according to the wobble carrier frequency signal. Theprotection circuit 36 generates reference signals to prevent noiseinterference. The decoder 30 according to the present invention providestwo types of decoding to the decoding circuit 40, in order to increasedata recognition. The decoding circuit 40 includes a cosine signalgenerator 42, a multiplier 44, an accumulator 46, a phase data processor48, and an ADIP unit detector 50. The operation of these devices isdescribed as follows.

Please refer to FIG. 6 showing the signals shown in FIG. 5. Since thewobble carrier frequency signal (DCOCLK) has a phase difference of 90degrees from the input wobble signal (ADIN), the cosine signal generator42 converts the wobble carrier frequency signal (DCOCLK) into afrequency signal (DCOCLK_COS) having the same phase as the input wobblesignal (ADIN). The multiplier 44 then multiplies the frequency signal(DCOCLK_COS) with the input wobble signal (ADIN). In phase encoding,since the frequency signal (DCOCLK_COS) and the input wobble signal(ADIN) have a phase difference of 180 degrees with respect to eachother, the product signal (MUL) is negative. Subsequently, theaccumulator 46 accumulates the product signals of each clock(DCO_FSCK_PEDGE) to obtain a quotient summation signal (qsum). The phasedata processor 48 determines whether the phase of the input wobblesignal (ADIN) changes or not to obtain a phase change signal(phase_chg). Finally, the ADIP unit detector 50 generates the ADIP unitsignal (ADIP_UNIT) being “0”, “1” or SYNC. The advantage of quotientsummation is that the input wobble signals are more resistant to noisesafter quotient summation. In addition, according to phase modulation,only when the wobble signals generated by the phase lock loop 32 arecontrolled in a specific error range can a less preciseanalog-to-digital converter (ADC) be used for generating the inputwobble signal. However, it is known by experience that the wobblesignals change in form due to defects of the disc or materialcharacteristic changes of the disc after writing data. Because of this,it is difficult to determine the ADIP unit signals even by quotientsummation. Therefore, the present invention provides a fuzzy comparemethod and a relative shape compare method to further improve therecognition of the ADIP unit signals.

Please refer to FIG. 7 showing the fuzzy compare method according to thepresent invention. Theoretically, the ADIP unit signal (ADIP_UNIT) mustbe “0”, “1” or SYNC. Thus, at the position where the ADIP unit signalsof the input wobble signal (ADIN) appear, that is, from the 84^(th)clock (fsck_cnt) to the 91^(th) clock, compare the phase change signal(phase_chg) of the input wobble signal (ADIN) with the patternsrepresenting the ADIP units “0”, “1” and SYNC (pat_0, pat_1, pat_s) ineach clock. If the patterns are the same as the phase change signal,gradually increase the pattern count signals (pat_0_cnt, pat_1_cnt,pat_s_cnt). If they are different, do not change the pattern countsignals. After completing the comparison in each clock, choose threepattern count signals having the maximum values to be the output valuesof the ADIP unit signal. Since the ADIP unit signals (being “0”, “1” andSYNC) are encoded by inputting 8 phase changes, the fuzzy compare methodallows any one of the 8 phase changes to be misjudged and the ADIP unitsignal closest to the input wobble signal can still be found. In FIG. 7,the phase change signal (phase_chg), determined by the quotientsummation signal (qsum), and the pattern representing ADIP unit “0”(pat_0) are different only during the 90^(th) clock. Thus the patterncount signal (pat_0_cnt) gets a maximum value so that the ADIP unitsignal (ADIP_UNIT) is determined as “0”.

Please refer to FIG. 8 showing the relative shape compare methodaccording to the present invention. When there is distortion or centerdeviation in the input wobble signal, the result of the quotientsummation signal (qsum) may have one or more phase changes to theincorrect value, so that the ADIP unit signal (ADIP_UNIT) cannot bedetermined correctly even using the fuzzy compare method. In this case,find the 4 clocks having the smallest quotient summation from the84^(th) clock (fsck_cnt) to the 91^(th) clock, and encode them as “1”and encode the rest as “0” in order to obtain sync pattern(sync_pattern). And then compare the patterns representing the ADIPunits “0”, “1” and SYNC (pat_0, pat_1, pat_s) with the sync pattern inorder to find the ADIP unit signal closest to the input wobble signal.In FIG. 8, 8 quotient summation count signals (q1_cnt to q8_cnt) can beobtained at the 92^(th) clock. The priorities of the 1^(st) quotientsummation count signal (q1_cnt) to the 8^(th) quotient summation countsignal (q8_cnt) are 5, 1, 3, 4, 2, 0, 7, 6, respectively. Wherein, thesmaller the value is, the larger the quotient summation is. Thus, encodethe 84^(th), the 87^(th), the 90^(th), and the 91^(st) clocks as “1”,and the 85^(th), the 86^(th), the 88^(th), and the 89^(th) clocks as“0”. In this way, the sync pattern (sync_pattern) obtained is1001_(—)0011. By comparing the sync pattern with the patternsrepresenting the ADIP unit “0”, “1” and SYNC encoded as 1000_(—)0011,1000_(—)1100, 1111_(—)0000, respectively, it can be determined thatthere is only one phase change between each other so that the ADIP unitsignal (ADIP_UNIT) can be determined as “0”.

Please refer to FIG. 9 showing a flowchart according to the presentinvention. In conjunction with the descriptions in FIG. 7 and FIG. 8,the method according to the present invention is as follows:

Step 210: Convert the wobble carrier frequency signal output by thephase lock loop 32 into the wobble carrier frequency signal with thesame phase as the input wobble signal by means of the cosine signalgenerator 42.

Step 220: Multiply the wobble carrier frequency signal output by thecosine signal generator 42 with the input wobble signal in order toobtain the product signal.

Step 230: Accumulate the product signals at every clock using theaccumulator 46 in order to obtain the quotient summation signal.

Step 240: Determine the phase change of the input wobble signalaccording to whether the quotient summation signal is positive ornegative using the phase data processor 48 in order to obtain the phasechange signal.

Step 250: Determine whether the phase change signal represents an ADIPunit. If yes, proceed to Step 270, and if no, proceed to Step 251.

Step 251: Execute the fuzzy compare method. Compare the phase changesignal with the plurality of ADIP patterns using the ADIP unit detector50, and determine the ADIP unit of the input wobble signal according tothe ADIP pattern closest to the phase change signal.

Step 260: Is the ADIP pattern closest to the phase change signal found(differing by only one clock)? If yes, proceed to Step 270, and if no,proceed to Step 261.

Step 261: Execute the relative shape compare method. Sequence thequotient summation signals at each clock using the ADIP unit detector50, select the plurality of clocks having smaller quotient summationsignals to encode in order to obtain the sync pattern, and then comparethe sync pattern with the plurality of ADIP patterns in order todetermine the ADIP unit of the input wobble signal.

Step 270: Output the ADIP unit of the input wobble signal.

Please refer to FIG. 10 showing a result table for experiments performedaccording to the present invention. The table in FIG. 10 shows ADIP unitlost error numbers obtained by three methods of different disc typeshaving different statuses. Wherein, method 1 is the quotient summationmethod, method 2 is the fuzzy compare method, and method 3 is the fuzzycompare method with the relative shape compare method. The larger thenumber is, the higher the error rate is. As shown by the table, theerror rate is obviously improved and less influenced by noise on thewobble signal after using method 2 and method 3. Please notice that therelative shape compare method can also be utilized separately, which hassimilar function with fuzzy compare method. However, the relative shapecompare method can only be used after 8 clocks have passed, while thefuzzy compare method can be used during these 8 clocks. As such, theoptimal combination is to compare the first 8 clocks using the fuzzycompare method, and then compare the rest using the relative shapecompare method. In this way, the smallest error rate can be realized asshown by method 3 in FIG. 10. Moreover, if the value of the ADIP unitsignal (ADIP_UNIT) cannot be determined by either the fuzzy comparemethod or the relative shape method, the ADIP unit signal will be markedas “unknown” and sent to the ECC block for ECC process.

As mentioned above, by means of the quotient summation signal obtainedfrom the input wobble signal using quotient summation, it is easier todetermine the position where the phase changes. The ADIP unit of theinput wobble signal can thereby be determined according to the phasechange signal obtained from the quotient summation signal. When thedetection of the phase change is incorrect, the present inventionprovides the fuzzy compare method and the relative shape compare methodfor modification. The difference between the two methods is that thefuzzy compare method executes comparison using the phase change signaldetermined from the quotient summation signal, while the relative shapecompare method finds clocks with smaller values from the quotientsummation signals to re-encode and then execute comparison.

In contrast to the prior art, the fuzzy compare method and the relativeshape compare method according to the present invention can improve theability of determining the ADIP unit of the wobble signals. Furthermore,since the ADIP decoding plays an important role in reading and writingDVD+R/RW discs, the present invention can increase the ability of theoptical disc drive of reading optical discs.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and the method may be madewhile retaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

1. A method for decoding address data of an optical disc drive fordecoding an input wobble signal into an address data unit signal, theoptical disc drive comprising a phase lock loop, a cosine signalgenerator, a multiplier, an accumulator, a phase data processor and anaddress data unit detector, the method comprising: (a) converting awobble carrier frequency signal output by the phase lock loop into awobble carrier frequency signal with the same phase as the input wobblesignal using the cosine signal generator; (b) multiplying the wobblefrequency signal, output by the cosine signal generator, with the inputwobble signal to obtain a product signal using the multiplier; (c)accumulating the product signals at each clock to obtain a quotientsummation signal using the accumulator; (d) determining phase changes ofthe input wobble signal according to whether the quotient summationsignal is positive or negative to obtain a phase change signal using thephase data processor; and (e) comparing the phase change signal with theplurality of address data patterns using the address data unit detector,and determining an address data unit signal according to the addressdata pattern closest to the phase change signal.
 2. The method of claim1, wherein Step (e) comprises comparing the phase change signal with thevalues of the plurality of address data patterns of each clock; whenthere is an address data pattern having the same value as the phasechange signal, adding a count number to the address data pattern; andeventually using the address data pattern having the most count numbersas the address data unit signal.
 3. The method of claim 1, furthercomprising: (f) sequencing the values of the quotient summation signalsat each clock using the address data unit detector, and selecting aplurality of clocks having smaller quotient summations in order toobtain a sync pattern; and (g) comparing the sync pattern with theplurality of address data patterns using the address data unit detector,and using the ADIP pattern closest to the sync pattern as the addressdata unit signal.
 4. The method of claim 1, wherein the optical discdrive is a DVD+R/RW drive and the address data is address in pre-groove(ADIP).
 5. A device for implementing the method of claim 1.